ABSTRACT. The effect of prolonged (2 h) hypocarbia on cerebral blood flow, oxygen delivery, extraction, and consumption was studied in eight, 1- to 4-day-old piglets. Hyperventilation to PaCO2 < 20 mm Hg acutely (30 min) decreased cerebral blood flow and oxygen oconsumption. Cerebral oxygen consumption was subsequently restored via increases in cerebral blood flow and thus, cerebral oxygen delivery. Cerebral oxygen extraction rose from a normocarbic baseline of 50 to 75% with acute hypocarbia and was maintained at this level. The percent decrease in blood flow to the cerebrum was greater than that to other brain regions during hypocarbia.